This invention relates to a scribe device for forming a scribe line on a flat plate-shaped workpiece.
The most primitive scribe device includes a holder, and a disc-shaped cutter rotatably disposed at a lower end of the holder. The peripheral edge of the cutter is sharpened. In this scribe device, by moving the holder with the cutter pressed against the surface of the workpiece, a scribe line is formed on the surface of the workpiece by the peripheral edge of the cutter.
In the above device, the nearby area of the scribe line on the workpiece is easily fractured because a large pressing load is imposed on the workpiece by the cutter. This makes it difficult to form a clear scribe line on the workpiece. In order to overcome this difficulty, the present applicant has developed a scribe device as disclosed in Japanese Patent Application Laid-Open No. H09-278473. This device includes a body, a plate spring (resilient member) one end of which is connected to the body, a piezo-actuator for feeding a vibration energy to this plate spring, and a scribe tool fixed to the other end of the plate spring. In this device, the scribe tool is pressed against the workpiece by the resiliently deformed plate spring. In that pressing state, when the piezo-actuator is driven while moving the body along the workpiece, the vibration energy of the piezo-actuator is transmitted to the scribe tool through the plate spring. By this, the scribe tool strikes the workpiece while moving along the workpiece surface, thus enabling to generate a continuous vertical a crack on the workpiece and hence enabling to form a scribe line thereon.
In the above device, the plate spring is intended to undertake such roles as to retain at a tip thereof the scribe tool, as to give a pressing load to the scribe tool so as to be imposed on the workpiece, and as to transmit vibrations from the piezo-actuator to the scribe tool.
However, since the plate spring has many roles, the above device is not suited to use for scribing a thin workpiece which is made of fragile material such as a silicone wafer, a semiconductor compound, or the like. That is, since the plate spring undertakes such roles as to retain the scribe tool and as to transmit vibrations, it is necessary to set the spring constant large. For this reason, an overly large pressing load is occasionally imposed on a thin workpiece. Moreover, the scribe tool is poor in followability with respect to fine irregularities formed on the workpiece, and the pressing load varies widely. Furthermore, since the vibrations of the piezo-actuator is transmitted to the scribe tool through the plate spring, it is difficult to transmit the vibrations in a stable manner. As a result, it is very difficult for this device to form a clear scribe line on a thin workpiece.
The present applicant has also developed another scribe device as disclosed in Japanese Patent Application Laid-Open No. 2001-48562. In this scribe device, a large mass including a body, a holder, a piezo-actuator, and the like is guided by a slide mechanism, floated and resiliently supported by a magnet. However, this device has the following problems. Since the workpiece is struck by a large mass, the impact given to the workpiece becomes overly large. Moreover, in order to retain a large mass, the spring constant for the magnet becomes large. Thus, followability with respect to fine irregularities formed on the workpiece is poor and the pressing load varies widely. As a result, even those devices are unable to form a clear scribe line on a thin workpiece.
In order to solve the above problems, a scribe device according to the present invention comprises (a) a body, (b) a holder rotatably supported by the body, (c) a scribe tool attached to one end part of the holder, (d) a vibration generating member disposed at the holder and for feeding a vibration energy to the scribe tool through the holder, (e) a resilient member one end of which is fixed to the holder, and (f) a pressing member disposed at the body and for pressing the resilient member for flexure, thereby giving a rotational force to the holder and thus giving a pressing load directing toward a workpiece to the scribe tool.
In the above construction, the resilient member undertakes only a role for giving a pressing load to be imposed on the workpiece to the scribe tool. but it does not undertake roles for retaining the scribe tool and for transmitting vibrations. For this reason, the spring constant of the resilient member can be set small and the pressing load can be reduced. Therefore, the scribe tool can follow the fine irregularities formed on the workpiece surface and the variation of the pressing load can be reduced. Furthermore, the vibrations coming from the vibration generating member can be transmitted from the holder to the scribe tool without through the resilient member in a stable manner. In addition, an impact load can be given to the workpiece with a comparatively small mass. As a result, a clear scribe line can be formed on a workpiece even if the workpiece is thin.
According to one embodiment of the above device, the body and the holder are respectively provided with mutually opposing receiving parts and the vibration generating member is disposed between those receiving parts. Owing to this arrangement, the vibration energy coming from the vibration generating member can surely be fed to the scribe tool.
In the above-mentioned one embodiment, the body is provided with an auxiliary resilient member serving as the receiving part of the body. Owing to this arrangement, it can be prevented to impose an overly large pressing load on the workpiece with the scribe tool climbed over the workpiece.
Preferably, the auxiliary resilient member is composed of a plate spring. Owing to this arrangement, the vibration energy can be transmitted to the scribe tool in a stable manner.
According to another embodiment of the above-mentioned device, the holder includes a first holder part rotatably supported by the body, and a second holder part rotatably supported by the first holder part, one end of the resilient member is fixed to the first holder part, the scribe tool is attached to one end of the second holder part, the first holder part and the second holder part are respectively provided with mutually opposing receiving parts, the vibration generating member is disposed between those receiving parts, and the vibration energy coming from the vibration generating member is fed to the scribe tool through the second holder part.
Also in the above-mentioned another embodiment, the same operation and effect as in the first embodiment can be obtained. In addition, the following operation and effect can also be obtained. That is, since the vibration generating member is disposed between the receiving parts of the first and second holder parts, no effect prevailed, under any circumstance, on the relation between the resilient force of the resilient member and the pressing load of the scribe tool to be imposed on the workpiece, and a desired pressing load can surely be obtained.
According to still another embodiment, preferably, the first holder part is provided with a pre-loading member, the pre-loading member is disposed, when viewed from the center of rotation of the second holder part with respect to the first holder part, on the opposite side to the vibration generating member, a pre-load serving as a compressing force is given to the vibration generating member by providing a rotational force to the second holder part. Owing to this arrangement, the vibration generating member can feed a vibration energy to the second holder part and scribe tool in a stable manner.
In the device of the present invention, preferably, the pressing member is composed of an adjustment screw capable of adjusting an amount of projection of a tip part thereof, and the tip part of the adjustment screw is abutted with the resilient member. According to this arrangement, by adjusting the amount of projection of the tip part of the adjustment screw, the resilient force of the resilient member can be adjusted and thus, the pressing load of the scribe tool with respect to the workpiece can be adjusted and therefore, an optimum scribing operation corresponding to the thickness, quality and the like of the workpiece can be performed.
More preferably, the holder is provided with an abutment part, the abutment part is disposed, when viewed from the center of rotation of the holder with respect to the body, on the opposite side to the scribe tool, and the body is provided with a load detecting member for detecting a load from the abutment part. According to this arrangement, by detection of the load which the load detecting member receives from the abutment part, adjustment can be made by correctly anticipating the pressing load of the scribe tool with respect to the workpiece.
Preferably, a product of the mass of one side of a rotation system including the holder with reference to the center of rotation and the distance between its center of gravity and the center of rotation is approximately equal to a product of the mass of the other side and the distance between its center of gravity and the center of rotation. Owing to this arrangement, it is possible to eliminate the effect of the holder, which would otherwise be prevailed on the pressing load of the scribe tool to be imposed on the workpiece.
In all the above-mentioned embodiments, the resilient member is preferably a plate spring. Owing to this arrangement, the pressing load to the scribe tool can be fed in a more stable manner, and the scribe tool can surely be followed to the fine irregularities formed on the workpiece surface.